例2设 少=n(x+e ),求小 1+2xe 解∵y 1+2xe dy x+e xe 例3设y=e-3 cos x,求d 解 ∴1-3x) 3e 1-3x cos x) sInx。 y'=cosx(3e)+e.(sin x dy=cos x(-3e1-3x5)+e 1-3x (sin x)lx e(3 cos x sin x )dx. Economic-mathematics 18-13 Wednesday, February 24, 2021Economic-mathematics 18- 13 Wednesday, February 24, 2021 例2 解 ln( ), . 2 y x e dy 设 = + x 求 , 1 2 2 2 x x x e xe y + +   = . 1 2 2 2 dx x e xe dy x x + +  = 例3 解 cos , . 1 3 y e x dy 设 = − x 求 ( ) 3 , (cos ) sin . 1 3 1 3 e e x x x x  = −  = − − −  dy  x e e x dx x x cos ( 3 ) ( sin ) 1 3 1 3  =  − +  − − − (3cos sin ) . 1 3 e x x dx x = − + − cos ( 3 ) ( sin ) 1 3 1 3 y x e e x x x   =  − +  − − −